Why is gestational age different from fetal age?
Gestational age counts from LMP, while fetal age counts from conception (~2 weeks later).
Health Fitness
Gestational Age Calculator
Calculate gestational age with your details.
Personalized estimate
Use realistic inputs for the most useful results.
What this calculator does
Gestational age measures pregnancy duration in weeks from the first day of the last menstrual period (LMP). Medical professionals use this standard dating system for prenatal care, developmental milestones, and due date calculation. Gestational age differs from fetal age by approximately 2 weeks.
How it works
Calculate days from LMP to current date, then convert to weeks and days. First trimester ultrasound can refine the estimate.
Formula
Gestational Age = (Current Date - LMP) ÷ 7 weeks. Full term = 37-42 weeks. Due date = LMP + 280 days.
Tips for using this calculator
- Know your exact LMP for best accuracy
- Early ultrasound (8-12 weeks) provides most accurate dating
- Gestational age ≠ fetal age (differs by ~2 weeks)
- Full term begins at 37 weeks
- Most babies arrive within 2 weeks of due date
Frequently asked questions
What if I don't know my LMP?
Early ultrasound can estimate gestational age within 3-5 days accuracy.
Is the due date accurate?
Only 4% deliver on exact due date. Most arrive within 2-week window.